Packed Bed Reactors (PBRs) Packed Bed Reactors (PBRs). Heterogenous catalytic reactors put emphasis on catalyst effectiveness factors and the heat and mass transfer implications. A fixed bed reactor is a cylindrical tube filled with catalyst pellets with reactants flowing through the bed and being converted into products. A trickle bed reactor is a fixed bed where liquid flows without filling the spaces between particles. A moving bed reactor has a fluid phase that passes up through a packed bed. Fixed-bed Reactor Fixed-bed reactors have long been used in process industries. They contain catalyst, typically in pellet form, packed in a static bed.
Comparison of the Effects of Fluidized-Bed and Fixed-Bed Reactors in Microwave-Assisted Catalytic Decomposition of TCE by Hydrogen. And there is an interactive relationship between the catalyst type and the reaction bed type. Faucher, Thermal modeling of microwave heated packed and fluidized bed catalytic reactors, Journal of Microwave Power and Electromagnetic Energy, vol. Uniform Particle Mixing: Due to the intrinsic fluid-like behavior of the solid material, fluidized beds do not experience poor mixing as in packed beds. In another approach you could distinguish between a fixed bed, a fluidised bed and an externally circulating bed. Fixed beds are used in the process industries as catalytic chemical reactors, adsorption/desorption beds, thermal regenerators, heat storage devices and pebble bed heaters. Heat transfer in fixed beds can be either a steady state or a transient process and various mathematical models have been proposed to describe transfer of heat between the fliud flowing through the fixed bed and the packing of the fixed bed.
Packed bed reactors are one of the most common reactors used in chemical processing applications. The space located between particles is described as macroporous structure of the bed, while pores inside the catalyst themselves form what is known as the microstructure. Multiphase catalytic packed-bed reactors (PBRs) operate in two modes: (1) trickle operation, with a continuous gas phase and a distributed liquid phase, and the main mass transfer resistance located in the gas, and (2) bubble operation, with a distributed gas. However, for three -phase catalytic reactors such as those employed for hydrotreating of middle distillates and heavy petroleum fractions, the reaction occurs between the dissolved gas and the liquid-phase reactant at the surface of the catalyst, and the choice of upflow versus downflow operation can be based on rational considerations regarding the limiting reactant at the operating conditions of interest (Dudukovic et al. In a TBR the catalyst bed is fixed (Figure 2.1), the flow pattern is much closer to plug flow, and the ratio of liquid to solid catalyst is small.